From: Richard Kaulfuss
Subject: Re: How to check for a 50 or 75 ohm connector
Date: Mon, 23 Dec 2002 01:05:15 +0000
References: <3E053579.AFE0BFDF@sympatico.ca> <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: Mon, 23 Dec 2002 01:05:40 +0000 (UTC)
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On Mon, 23 Dec 2002 00:12:08 GMT, DarkMatter
> Impedance is a reactive term. That means capacitance and
>inductance. Guess which coaxial cable exhibit that determines their
>impedance the most?
> Of course we are talking about capacitance. Have you ever seen an
>HV transmission coax? It looks JUST LIKE a large diameter coax for an
>old CB radio set.
> When one applies the juice through it, however, the thing jumps.
>That is a physical contraction due to capacitive charging.
> We have always been talking about a capacitor. If one looks at a
>circuit where there is a jumper between two circuit element, and that
>jumper is coaxial, it appears as a capacitor to the circuit.
>Every time. Unless used to pass DC, of course. Even in that case, it
>does charge up. I can make various HV capacitive loads for testing HV
>supplies by simply changing the cable length.
> It IS basic electronics. Capacitive reactance is called impedance.
I'm beginning to suspect you don't actually understand the concepts
of transmission lines and characteristic impedance.
>>If I connect
>>two 50 ohm BNC cables via a 75 ohm coupler it will exhibit a worse
>>return loss than if I use a 50 ohm coupler. If I really feel bored and
>>have nothing useful to do tomorrow then I might perform this experiment
>>with an SNA, I won't confuse you with a VNA and a sliding termination.
> Hahahah... whatever.
Hmm...thought as much.